A machine for molding of steel fabric reinforced concrete pipes is known, consisting of an external mold and a core tube, the mold and tube being arranged vertically and coaxially in such way that they can be displaced concentrically in relation to each other. At the upper end of the external mold a funnel is mounted separably, forming an extension of the external mold. The core tube, however, is provided at its lower end with a stop collar mounted separably and fitted to the internal diameter of the external mold so that there is formed between the external mold and the core tube, a ring-shaped space, whereby the external mold and the funnel can be vibrated together.
A disadvantage of such a machine is the lack of lubrication of the inner surface of the external which makes it difficult to remove the steel fabric reinforced concrete pipe produced in the molding process from the inside of the outer mold. A further disadvantage is also that an important part of energy used for vibrating is absorbed by the external mold together with the funnel which makes it necessary to employ vibrators with great force for generating the vibrations.